The present invention relates in general to salvage techniques for costly machine components whereby the damaged or worn portion of the component is replaced by a specially-made sleeve or insert. The present invention also relates in general to the final design of the reworked component as a result of performing the salvage technique.
More particularly the present invention relates to a salvage technique for a turbocharger bearing housing where a portion of the outside diameter of the housing has been damaged in the area contacted by the heat shield. Further, the present invention relates to the design of the turbocharger bearing housing which results from the salvage technique.
Salvage techniques to repair or recondition damaged or worn surfaces or portions of the component or device are known in the art. One technique which may be employed is the method of metal deposit or plating in order to build up a worn surface and bring it back to its near original dimensions. Another technique is to first machine down the worn area in order to prepare it for the receipt of a specially machined replacement or repair member. The repair member when used to build up an outside diameter surface includes an inside diameter surface or contour which is designed to match, often with an interference fit, the machined down surface or portion of the worn part. The repair member also includes an outer surface or outside surface portion which is contoured in order to simulate the original size and shape of the worn area.
In some applications and with some types of components it may not be possible or it may not be preferred to machine the completed assembly. Under such circumstances the sleeve or insert member used for repair of the worn or damaged part is precisely sized and shaped so that no post-assembly machining is required in order to restore the damaged part back to all of its original dimensions. In these situations there is a significant focus on the sizes, shapes and tolerances of the base component part while removing or preparing the worn area. There is also a significant focus on the sizes, shapes and tolerances of the repair member which is separately machined and designed to slip into or over the prepared portion of the component part. Consider for example U.S. Pat. No. 2,752,668 issued to Sheen on Jul. 3, 1956. The base part disclosed in this reference is a piston head portion 10 and the machined repair member is ring 16. The patent specification focuses on the critical selection of dimensions and tolerances so that "no machining was necessary after completion of the shrinkage" of the ring onto the piston head portion.
The concept of metal removal from the worn part and heat shrinking or pressing on a repair member is not limited to outside diameters and cylindrical shapes as disclosed in the Sheen patent. Consider U.S. Pat. No. 4,691,423 which issued to Willyard, Jr. on Sep. 8, 1987. The Willyard patent discloses a method for remanufacturing a compressor housing which involves machined removal of the inlet throat which has been damaged due to contact with the compressor wheel. A separately manufactured and carefully sized throat insert is provided and assembled into the compressor housing by heating the compressor housing to temporarily create a larger diameter. An alternative method of cooling the insert to reduce its size is also disclosed as a suitable method for assembly.
The general repair technique disclosed in Willyard, Jr. is not restricted to compressor housings. U.S. Pat. No. 4,852,236 which issued to Emery on Aug. 1, 1989 discloses the use of a insert to repair an inside diameter surface which has become worn or damaged. In Emery the salvage technique is applied to a worn wobbler housing for a constant-speed drive. While the new wear plate which is assembled into the housing is of a generally cylindrical nature, like the sleeve in Sheen, each specific application for a replacement or insert necessitates special consideration and design restrictions.
One consideration includes the size, shape and strength of the worn part relative to what surfaces can be machined down and how much can be taken off without adversely affecting the continued use of the assembly after repair or salvage. Another consideration is whether the insert or ring to be assembled to the main component part can be machined after assembly. In Sheen it was apparently preferred not to machine the remanufactured piston after assembly of the ring sleeve and thus the various dimensions and tolerances had to be more tightly controlled. In the patents issued to Willyard and Emery, some dimensions are more important than others and the salvage technique employed in each instance must be specifically and uniquely tailored for the environment and application of the completed part.
The concept of being uniquely tailored for the specific environment and application applies to the present invention. In the present invention the worn or damaged end of the turbocharger bearing housing is repaired by carefully and precisely machining selected surfaces and then installing a salvage sleeve to build back up the material thickness of the machine surfaces. After assembly of the sleeve to the bearing housing the outside diameter of the sleeve is turned down thereby both shaping it and bringing the dimensions back in line to those of the originally manufactured housing.
More specifically the environment for the present invention is a diesel engine turbocharger bearing housing. Due to vibration and thermal expansion the V-band clamp may become loose and if this occurs the heat shield will be allowed to move radially. This in turn causes damage to the area of the housing which contacts the heat shield. Left unrepaired this type of failure mode can lead to catastrophic failure of the turbocharger. The salvage technique described herein enables the user to repair the damaged portion and reestablish the original part dimensions and specifications.